Writing instrument



FIG. 1 is a front view of a writing instrument showing my new design;

FIG. 2 is a side view thereof;

FIG. 3 is another side view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a perspective front view thereof. 

The ornamental design for a writing instrument, as shown and described. 